Systems and methods for treating fractured or diseased bone using expandable bodies

ABSTRACT

Systems and methods treat fractured or diseased bone by deploying more than a single therapeutic tool into the bone. In one arrangement, the systems and methods deploy an expandable body in association with a bone cement nozzle into the bone, such that both occupy the bone interior at the same time. In another arrangement, the systems and methods deploy multiple expandable bodies, which occupy the bone interior volume simultaneously. Expansion of the bodies form cavity or cavities in cancellous bone in the interior bone volume.

RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 10/958,600 filed 5 Oct. 2004, which is a divisional of U.S.patent application Ser. No. 09/754,451 filed 4 Jan. 2001, now U.S. Pat.No. 6,899,719 which is a continuation of U.S. patent application Ser.No. 08/871,114 filed 9 Jun. 1997, now U.S. Pat. No. 6,248,110, which isa continuation-in-part of U.S. patent application Ser. No. 08/659,678,filed Jun. 5, 1996, now U.S. Pat. No. 5,827,289, which is acontinuation-in-part of U.S. patent application Ser. No. 08/485,394,filed Jun. 7, 1995 (now abandoned), which is a continuation-in-part ofU.S. patent application Ser. No. 08/188,224, filed Jan. 26, 1994entitled, “Improved Inflatable Device For Use In Surgical ProtocolRelating To Fixation Of Bone” (now abandoned), all of which are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to the treatment of bone conditions in humans andother animals.

BACKGROUND OF THE INVENTION

When cancellous bone becomes diseased, for example, because ofosteoporosis, avascular necrosis, or cancer, the surrounding corticalbone becomes more prone to compression fracture or collapse. This isbecause the cancellous bone no longer provides interior support for thesurrounding cortical bone.

There are 2 million fractures each year in the United States, of whichabout 1.3 million are caused by osteoporosis alone. There are also otherbone disease involving infected bone, poorly healing bone, or bonefractured by severe trauma. These conditions, if not successfullytreated, can result in deformities, chronic complications, and anoverall adverse impact upon the quality of life.

U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose apparatus and methodsfor the fixation of fractures or other conditions of human and otheranimal bone systems, both osteoporotic and non-osteoporotic. Theapparatus and methods employ an expandable body to compress cancellousbone and provide an interior cavity. The cavity receives a fillingmaterial, which hardens and provides renewed interior structural supportfor cortical bone.

The better and more efficacious treatment of bone disease that thesePatents promise can be more fully realized with improved systems andmethods for making and deploying expandable bodies in bone.

SUMMARY OF THE INVENTION

The invention provides improved systems and methods for treating bone,including vertebral bodies, as well as in other bone types, using one ormore expandable bodies.

One aspect of the invention provides systems and methods for treatingbone using an expandable wall in association with a nozzle fordischarging a material. According to this aspect of the invention, thesystems and methods insert both the body and the nozzle into a bonehaving cortical bone surrounding an interior volume occupied, at leastin part, by cancellous bone. The systems and methods causing the body toassume an expanded geometry while occupying the interior volume in thepresence of the nozzle to compact cancellous bone and form a cavity inthe interior volume. The systems and methods convey a material fordischarge through the nozzle into the cavity at least partially whilethe body occupies the interior volume.

In a preferred embodiment, the systems and methods convey bone cementfor discharge through the nozzle, while the body is in the expandedgeometry or a partially expanded geometry. The systems and methods canalso cause the expanded geometry of the body to decrease in volume inrelation to volume of material discharged by the nozzle into the cavity.

In one embodiment, the expandable body and nozzle are deployedseparately into the targeted bone. In a preferred embodiment, theexpandable body and nozzle form a integrated tool and are deployedsimultaneously into the targeted bone.

Another aspect of the invention provides systems and methods fortreating bone using first and second expandable bodies. The firstexpandable body is inserted into the interior bone volume through afirst access path in cortical bone. The second expandable body isinserted into the same interior bone volume through a second access pathin cortical bone different than the first access path. The systems andmethods cause each of the bodies to assume an expanded geometry forjointly compacting cancellous bone to form a cavity in the interiorvolume.

In one embodiment, the first and second access paths comprise differentipsilateral posterolateral accesses. In another embodiment, the firstand second access paths comprise different transpedicular accesses. Inyet another embodiment, the first a second access paths comprise atranspedicular access and a postereolateral access.

Another aspect of the invention provides a body for insertion into abone, which comprises two expandable zones. The first zone assumes anelongated expanded geometry. The elongated geometry presents a firstdimension, which extends substantially across the interior volume, toform a barrier within the interior volume. The elongated geometry alsopresents a second dimension less than the first dimension, which leavesa region of substantially uncompacted cancellous bone extending from thebarrier within the interior volume. The second expandable zone assumes adifferent expanded geometry, which compacts cancellous bone to form acavity in the region. The barrier formed by the first zone directsexpansion of the second zone in the region away from the first zone.

In one embodiment, the first and second expandable zones compriseseparate expandable assemblies. In another embodiment, the first andsecond expandable zone comprise parts of a single expandable assembly.

Features and advantages of the inventions are set forth in the followingDescription and Drawings, as well as in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the spinal column of a human;

FIG. 2 is coronal view of a lumbar vertebra, partially cut away and insection, taken generally along line 2-2 in FIG. 1;

FIG. 3 is a vertical section of lumbar vertebrae;

FIG. 4 is a plan view of a probe including a catheter tube carrying anexpandable body intended to treat bone;

FIGS. 5A to 5P are a series of coronal views of a vertebra, partiallycut away and in section, showing the steps of introducing, viatranspedicular access, an expandable body to compress cancellous boneand create a cavity within a vertebral body, and of then conveying afilling material into the cavity to restore interior integrity tocortical bone;

FIG. 5Q is a lateral view, with parts broken away, of the vertebra shownin coronal view in FIG. 5P;

FIG. 6 is a coronal view of a vertebral body in which an expandablebody, restrained by an external sealing element, compresses cancellousbone to form a cavity;

FIG. 7 is a coronal view, partially broken away and in section, of avertebral body in which an expandable body is being collapsed afterhaving formed a cavity, while an injector tip, also within the vertebralbody, is simultaneously injecting filling material into the cavity;

FIG. 8A is a coronal view of a vertebral body, partially broken away andin section, showing a tool that integrates an injector tube and anintegral expandable body to create a cavity in cancellous bone, and alsoshowing the injection of filling material simultaneous with collapse ofthe expandable body;

FIG. 8B is a side view of the tool shown in FIG. 8A, located outsidebone;

FIG. 8C is sectional view of the tool shown in FIG. 8B, taken generallyalong line 8C-8C in FIG. 8B;

FIG. 9 is a coronal view of a vertebral body showing multiple expandablebodies separately introduced by transpedicular approach;

FIG. 10 is a view of the distal end of a probe in which two cathetertubes, each carrying an expandable body, are joined to form a symmetricarray, when substantially expanded outside a bone;

FIG. 11 is a view of the distal end of a probe in which two cathetertubes, each carrying an expandable body, are joined to form anasymmetric array, when substantially expanded outside a bone;

FIG. 12 is a coronal view, partially broken away and in section, of avertebral body into which multiple expandable bodies have been deployedby dual transpedicular access;

FIG. 13 is a coronal view of a vertebral body, partially broken away andin section, into which multiple expandable bodies have been deployed bycontralateral posterolateral access;

FIG. 14 is a coronal view of a vertebral body, partially broken away andin section, in which multiple expandable bodies have formed multiplecavities which join to form a single cavity to receive filling material;

FIG. 15 is a coronal view of a vertebral body, partially broken away andin section, in which multiple expandable bodies have formed multipleseparate cavities to receive filling material;

FIG. 16 is an anterior-posterior view of a region of the spine, showingmultiple expandable bodies present within a targeted vertebral bodyusing ipsilateral postereolateral access;

FIG. 17 is an anterior-posterior view of a vertebral body, partiallybroken away and in section, in which multiple expandable bodies,introduced using ipsilateral postereolateral access, have formedmultiple cavities which are joined to form a single cavity to receivefilling material;

FIG. 18 is an anterior-posterior view of a vertebral body, partiallybroken away and in section, in which multiple expandable bodies,introduced using an ipsa posterolateral access, have formed multipleseparate cavities to receive filling material;

FIG. 19 is a coronal view of a vertebral body, partially broken away andin section, in which multiple expandable bodies have been introduced byboth transpedicular and posterolateral access;

FIG. 20 is a perspective view of one representative embodiment of anexpandable body having a stacked doughnut-shaped geometry;

FIG. 21 is a view of another representative embodiment of an expandablebody having an oblong-shaped geometry;

FIG. 22 is an elevation view of another representative embodiment of anexpandable body showing three stacked bodies and string-like restraintsfor limiting the expansion of the bodies during inflation;

FIG. 23 is a perspective view of another representative embodiment of anexpandable body having a kidney bean-shaped geometry;

FIG. 24 is a top view of another representative embodiment of anexpandable body having a kidney bean-shaped geometry with severalcompartments by a heating element or branding tool;

FIG. 25 is a cross-sectional view taken along line 25-25 of FIG. 24;

FIG. 26 is a perspective, lateral view of a vertebral body, partiallybroken away to show the presence of an expandable body, and also showingthe major reference dimensions for the expandable body;

FIG. 27 is a dorsal view of a representative expandable body having ahumpback banana-shaped geometry in use in a right distal radius;

FIG. 28 is a cross sectional view of the expandable body shown in FIG.27, taken generally along line 28-28 of FIG. 27;

FIG. 29A is a representative expandable body having a spherical shapewith a base, located in a proximal humerus and viewed from the front(anterior) of the left proximal humerus;

FIG. 29B is a representative expandable body having a cylindrical shape,located in a proximal humerus and viewed from the front (anterior) ofthe left proximal humerus;

FIG. 30A is a representative embodiment of an expandable body located,as shown in a front (anterior) view of the proximal tibia, introducedbeneath the medial tibial plateau;

FIG. 30B is a side elevation view of the expandable body shown in FIG.30A;

FIG. 30C is a top perspective view of the expandable body shown in FIG.30A, showing its generally cylindrical geometry;

FIG. 31 is a top plan view of another representative embodiment of anexpandable body for use in treating tibial plateau fractures, having agenerally elliptical geometry;

FIG. 32 is a side view of multiple expandable bodies stacked on atopanother for use, for example, in treating tibial plateau fractures;

FIG. 33 is another representative embodiment of an expandable bodyhaving an egg-shaped geometry located, as shown in a front (anterior)view of the proximal tibia, introduced beneath the medial tibialplateau;

FIG. 34 is a representative embodiment of an expandable body having aspherical-shaped geometry for treating avascular necrosis of the head ofthe femur (or humerus), which is shown from the front (anterior) of theleft hip;

FIG. 35 is a side view of another representative embodiment of anexpandable body having a hemispherically-shaped geometry for treatingavascular necrosis of the head of the femur (or humerus);

FIG. 36A is a view of a representative expandable body having abent-geometry for preventing hip fracture, as seen from the front(anterior) of the left hip;

FIG. 36B is a view of multiple expandable bodies individually deployedthrough multiple access points into the left hip for preventing hipfracture;

FIG. 37A is a view of a representative expandable body having anasymmetric bow tie-shape for use in treating fracture of the calcaneusbone, shown in lateral view within the calcaneus;

FIG. 37B is a perspective top view of the expandable body shown in FIG.37A when substantially expanded outside the calcaneus;

FIG. 38 shows a representative embodiment of an expandable body having aspherical or egg-shaped geometry shown in lateral view deployed withinthe calcaneus;

FIGS. 39A to 39D show a multiple stage process of introducing fillingmaterial into a cavity formed by an expandable body in cancellous bone,to prevent or impede flow or seepage of filling material from theinterior of the bone;

FIG. 40 is an elevation view of an injector tip for filling material,over which a mesh is draped, which, when deployed in a cavity formed byan expandable body, impedes or prevents seepage of the material from thecavity;

FIG. 41 is a coronal view of a vertebra, with parts broken away and insection, showing the deployment of the mesh shown in FIG. 40 within thevertebral body;

FIGS. 42A to 42C are schematic illustrations of a representative methodand system for delivering a therapeutic substance to a bone using anexpandable body;

FIG. 43 is an illustration of the human skeleton, showing regions oflong bone that can be treated using expandable bodies;

FIG. 44 is a representative embodiment of multiple expandable bodieslocated, as shown in a front (anterior) view, within the proximal tibia,both introduced beneath the medial tibial plateau, one of the bodiesbeing substantially expanded to form an interior barrier and serve as aplatform for the other body, which is shown substantially collapsed;

FIG. 45 is a front (anterior) view of the multiple expandable bodies,shown in FIG. 44, with both bodies in substantially expanded conditionsto form a cavity within the proximal tibia beneath the medial tibialplateau;

FIG. 46 is an enlarged front (anterior) perspective view of the multipleexpandable bodies shown in FIG. 45, with the lower expandable bodyserving as a platform for the upper expandable body;

FIG. 47 is diagrammatic view of a system for harvesting bone marrow in abone-marrow producing bone using an expandable body;

FIG. 48 is a section view of the catheter tube associated with thesystem shown in FIG. 48, taken generally along line 48-48 of FIG. 47;and

FIG. 49 is an enlarged view of the expandable body associated with thesystem shown in FIG. 47 inside a bone for the purpose of harvesting bonemarrow.

The invention may he embodied in several forms without departing fromits spirit or essential characteristics. The scope of the invention isdefined in the appended claims, rather than in the specific descriptionpreceding them. All embodiments that fall within the meaning and rangeof equivalency of the claims are therefore intended to be embraced bythe claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This Specification describes new systems and methods to treat bonesusing expandable bodies. The use of expandable bodies to treat bones isdisclosed in U.S. Pat. Nos. 4,969,888 and 5,108,404, which areincorporated herein by reference. Improvements in this regard aredisclosed in U.S. patent application Ser. No. 08/188,224, filed Jan. 26,1994; U.S. patent application Ser. No. 08/485,394, filed Jun. 7, 1995;and U.S. patent application Ser. No. 08/659,678, filed Jun. 5, 1996,which are each incorporated herein by reference.

The new systems and methods will be first described with regard to thetreatment of vertebra. It should be appreciated, however, the systemsand methods so described are not limited in their application tovertebrae. As will be described in greater detail later, the systems andmethods are applicable to the treatment of diverse bone types.

I. Treatment of Vertebral Bodies

As FIG. 1 shows, the spinal column 10 comprises a number of uniquelyshaped bones, called the vertebrae 12, a sacrum 14, and a coccyx 16(also called the tail bone). The number of vertebrae 12 that make up thespinal column 10 depends upon the species of animal. In a human (whichFIG. 1 shows), there are twenty-four vertebrae 12, comprising sevencervical vertebrae 18, twelve thoracic vertebrae 20, and five lumbarvertebrae 22.

When viewed from the side, as FIG. 1 shows, the spinal column 10 formsan S-shaped curve. The curve serves to support the head, which is heavy.In four-footed animals, the curve of the spine is simpler.

As FIGS. 1 to 3 show, each vertebra 12 includes a vertebral body 26,which extends on the anterior (i.e., front or chest) side of thevertebra 12. As FIGS. 1 to 3 show, the vertebral body 26 is in the shapeof an oval disk. As FIGS. 2 and 3 show, the vertebral body 26 includesan exterior formed from compact cortical bone 28. The cortical bone 28encloses an interior volume 30 of reticulated cancellous, or spongy,bone 32 (also called medullary bone or trabecular bone). A “cushion,”called an intervertebral disk 34, is located between the vertebralbodies 26.

An opening, called the vertebral foramen 36, is located on the posterior(i.e., back) side of each vertebra 12. The spinal ganglion 39 passthrough the foramen 36. The spinal cord 38 passes through the spinalcanal 37.

The vertebral arch 40 surrounds the spinal canal 37. The pedicle 42 ofthe vertebral arch 40 adjoins the vertebral body 26. The spinous process44 extends from the posterior of the vertebral arch 40, as do the leftand right transverse processes 46.

A. Deployment of an Expandable Body

FIG. 4 shows a tool 48 for preventing or treating compression fractureor collapse of a vertebral body using an expandable body.

The tool 48 includes a catheter tube 50 having a proximal and a distalend, respectively 52 and 54. The distal end 54 carries an expandablebody 56.

The body 56 includes an exterior wall 58, which, in FIG. 4, is shown ina collapsed geometry. The collapsed geometry permits insertion of thebody 56 into the interior volume 30 of a targeted vertebral body 26.

The insertion of the body 56 into the interior volume 30 of a targetedvertebral body 26 can be accomplished in various ways. FIGS. 5A to 5Qshow the insertion of the body 56 using a transpedicular approach, whichcan be performed either with a closed, mininimally invasive procedure orwith an open procedure.

In the described procedure, a patient lies on an operating table, whilethe physician introduces a conventional spinal needle assembly 60 intosoft tissue in the patient's back. The patient can lie facedown on thetable, or on either side, or at an oblique angle, depending upon thephysician's preference. Indeed, the procedure can be performed throughan open anterior procedure or an endoscopic anterior procedure, in whichcase the tool 48 may be introduced from the anterior aspect of thevertebral body.

The spinal needle assembly 60 comprises a stylet 62 slidable housedwithin a stylus 64. The assembly 60 typically has, for example, about an18 gauge diameter. Other gauge diameters can and will be used toaccommodate appropriate guide pins, as will be described in greaterdetail later.

Under radiologic, CT, or MRI monitoring, the physician advances theassembly 60 through soft tissue (designated S in FIG. 5A) down to andinto the targeted vertebra 12, as FIG. 5A shows. The physician willtypically administer a local anesthetic, for example, lidocaine, throughassembly 60. In some cases, the physician may prefer other forms ofanesthesia.

The physician directs the spinal needle assembly 60 to penetrate thecancellous bone 32 of the targeted vertebra 12. Preferably the depth ofpenetration is about 60% to 95% of the vertebral body 26.

FIG. 5A shows gaining access to cancellous bone 32 through the pedicle42, which is called transpedicular access. However, posterolateralaccess, through the side of the vertebral body 12 (designated P-L andshown in phantom lines in FIG. 5A), may he indicated, if a compressionfracture has collapsed the vertebral body 26 below the plane of thepedicle 42, or for other reasons based upon the preference of thephysician.

After positioning the spinal needle assembly 60 in cancellous bone 32,the physician holds the stylus 64 and withdraws the stylet 62 (see FIG.5B). Still holding the stylus 64, the physician slides a guide pin 66through the stylus 64 and into the cancellous bone 32 (see FIG. 5C). Thephysician now removes the stylus 64, leaving the guide pin 66 deployedwithin the cancellous bone 32, as FIG. 5D shows.

As FIG. 5E shows, the physician makes a small incision (designated I inFIG. 5E) in the patient's back to accommodate a trocar 68. The physicianinserts the trocar 68 through the soft tissue S along the guide pin 66down to the pedicle 42. The physician taps the distal end 70 of thetrocar 68 into the pedicle 42 to secure its position.

As FIG. 5F shows, the physician next slides an outer guide sheath 72over the trocar 68. The distal end 74 of the outer guide sheath 72 islikewise tapped into the pedicle 42. The physician removes the trocar68, leaving the guide pin 66 and outer guide sheath 72 in place, as FIG.5G shows. Alternatively, the trocar 68 and guide sheath 72 can beintroduced together in one step.

As FIG. 5H shows, the physician advances a drill bit 76 (for example, 5mm in diameter) over the guide pin 66 through the outer guide sheath 72.Under X-ray control (or using another external visualizing system), thephysician operates the drill bit 76 to open a passage 78 through thepedicle 42 and into the cancellous bone 32. The drilled passage 78preferable extends no more than 95% across the vertebral body 26.

As FIG. 5I shows, the physician removes drill bit 76 and guide pin 66,leaving the outer guide sheath 72. The passage 78 made by the drill bit76 remains, passing through the pedicle 42 and into the cancellous bone32.

As FIG. 5J(1) shows, the physician next advances the catheter tube 50and expandable body 56 through the outer guide sheath 72 and into thedrilled passage 78 in the cancellous bone 32. As best shown in FIG.5J(2), the body 56 is maintained in a straightened, collapsed conditiondistally beyond the end of the catheter tube 50 during transport throughthe guide sheath 72 and into the drilled passage 78 by a generallyrigid, external protective sleeve 73, which surrounds the body 56.Alternatively, an internal stiffening member (not shown) can extendwithin the body 56, to keep the body 56 in the desired distallystraightened condition during passage through the guide sheath 72. Oncethe body 56 is located in the desired location within the passage 78,the physician pulls the sleeve 73 back, to uncover the body 56. Theexpandable body 56 can be dipped into thrombin prior to its introductioninto the vertebral body 26 to facilitate in situ coagulation.

The materials for the catheter tube 50 are selected to facilitateadvancement of the body 56 into cancellous bone through the guide sheath72. The catheter tube 50 can be constructed, for example, using standardflexible, medical grade plastic materials, like vinyl, nylon,polyethylenes, ionomer, polyurethane, and polyethylene tetraphthalate(PET). The catheter tube 50 can also include more rigid materials toimpart greater stiffness and thereby aid in its manipulation. More rigidmaterials that can be used for this purpose include Kevlar™ material,PEBAX™ material, stainless steel, nickel-titanium alloys (Nitinol™material), and other metal alloys.

Once the protective sheath 73 is withdrawn, the wall 58 of the body 56is capable of assuming an expanded geometry within the interior volume30 (generally shown in FIG. 5K(1)). To accommodate expansion of the body56, the catheter tube 50 includes a first interior lumen 80 (see FIG.4). The lumen 80 is coupled at the proximal end of the catheter tube 50to a pressurized source of fluid 82. The fluid 82 is preferablyradio-opaque to facilitate visualization. For example, Renograffin™ canbe used for this purpose.

The lumen 80 conveys the fluid 82 into the body 56 under pressure. As aresult, the wall 58 expands, as FIG. 5K(1) shows. Because the fluid 82is radio-opaque, body expansion can be monitored fluoroscopically orunder CT visualization. Using real time MRI, the body 56 may be filledwith sterile water, saline solution, or sugar solution.

Expansion of the wall 58 enlarges the body 56 and compacts cancellousbone 32 within the interior volume 30. As FIG. 5K(2) shows, the presenceof the sheath 73 serves to keep the proximal end of the body 56 awayfrom edge-contact with the distal end of the catheter tube 50.

The compaction of cancellous bone 32 forms a cavity 84 in the interiorvolume 30 of the vertebral body 26. The compaction of cancellous bonealso exerts interior force upon cortical bone, making it possible toelevate or push broken and compressed bone back to or near its originalprefracture position. Using a single transpedicular access (as FIG.5K(1) shows), the cavity 84 occupies about one-half of the interiorvolume 30. As will be described in greater detail later, using multipleaccesses, e.g., one through each pedicle, a cavity 84 occupyingsubstantially all of the interior volume 30 can be created.

As FIG. 4 shows, the proximal end of the catheter tube 50 is preferablycoupled by tubing to a source of negative air pressure 86. The negativepressure is conveyed through a second interior lumen 81 to one or moresuction holes 88 on the distal end of the catheter tube 50. Prior to andduring the expansion of the body 56, suction is applied to remove fatsand other debris through the suction holes 88 for disposal. A separatesuction-irrigation tool can be deployed through the guide sheath 72 forthis purpose, if desired.

The body 56 is preferably left inflated for an appropriate waitingperiod, for example, three to five minutes, to allow coagulation insidethe vertebral body 26. After the appropriate waiting period, thephysician collapses the body 56 and removes it through the outer guidesheath 72 (see FIG. 5L). To facilitate removal, the exterior surface ofthe body 56 can be treated, e.g., by ion beam-based surface treatment,to reduce friction during passage through the outer guide sheath 72. AsFIG. 5L shows, upon removal of the body 56, the formed cavity 84 remainsin the interior volume 30.

A suction-irrigation tool (not shown) can be introduced through theouter guide sheath 72, to further flush and clear debris from the formedcavity 84 after removal of the body 56.

As FIG. 5M shows, an injector nozzle or tip 90, coupled by an injectortube 92 to an injector gun 94, is inserted through the outer guidesheath 72 into the formed cavity 84. The injector gun 94 carries afilling material 96. The filling material 96 comprises, for example,methylmethacrylate cement or a synthetic bone substitute.

The injector gun 94 can comprise a cement gun made, for example, byStryker Corporation (Kalamazoo, Mich.). This particular injector gun 94has a manually operated injection grip 98 with a mechanical advantage ofabout 9 to 1. Other injection guns may be used, having more or lessmechanical advantage. Non-manually operated injection guns can also beused.

The injector tip 90 can be, for example, about 4.9 mm in diameter, toaccommodate the flow a relatively viscous material 96 into the cavity84.

As FIG. 5M shows, the injector gun 94 pushes the filling material 96into the cavity 84. While injecting the material 96, the physicianpreferably begins with the injector tip 90 positioned at the anteriorregion of the cavity 84 (as FIG. 5M shows). The physician progressivelymoves the tip 90 toward the posterior region of the cavity 84 (as FIG.5N shows), away from the flow of the material 96 as it enters and fillsthe cavity 84. The physician observes the progress of the injectionfluoroscopically.

The physician can also check, using, for example, x-ray, for leakage ofthe material through cortical bone 28. Systems and methods for impedingor preventing such leakage will be described in greater detail later.

The physician flows material 96 into the cavity 84, until the material96 reaches the distal end 74 of the outer guide sheath 72 (as FIG. 5Oshows).

Upon removing the injector tube 92 from the outer guide sheath 72, thephysician may, if necessary, tamp residual filling material 96 from thedistal end 74 of the outer guide sheath 72 into the cavity 84. Iffluoroscopic examination reveals void regions in the cavity 84, thephysician may again insert the injector tube 92 to add more fillingmaterial 96 into the cavity 84.

FIG. 7 shows an alternative technique for filling the cavity. In thistechnique, the injector tip 90 occupies the cavity 84 while theexpandable body 56 is collapsing within the cavity 84. As the body 56collapses, the tip 90 injects material 96 into the part of the cavity 84that the collapsing body 56 no longer occupies. The increasing volume ofthe cavity 84 not occupied by the collapsing body 56 is therebyprogressively filled by an increasing volume of material 96. Thepresence of the body 56, partially expanded while the tip 90 injects thematerial 96, serves to compact and spread the injected material 96within the cavity 84.

As filling of the cavity 84 progresses, preferably under fluoroscopicmonitoring, the physician progressively retracts the injector tip 90from the anterior region of the cavity 84, toward the outer guide sheath72, allowing the material 96 to progressively enter and fill the cavity84 with the collapse of the body 56.

FIGS. 8A to 8C show a preferred embodiment of a tool 650 whichintegrates the injection tube and expandable body in a single structure.As FIG. 8B shows, the tool 650 includes a catheter tube 652 having aproximal end 654 and a distal end 656. The distal end carries anexpandable body 662.

As FIG. 8C shows, the catheter tube 652 has concentric inner and outerlumens, respectively 658 and 660. The inner lumen 658 communicates, byproximal tubing 664, with an injector gun 94, of the type previouslydescribed. The inner lumen 658 also communicates with an injector nozzleor tip 666 at the distal catheter tube end 656. Operation of the gun 94serves to inject filling material 96 through the nozzle 666 (as FIG. 8Ashows).

The outer lumen 660 communicates, via proximal tubing 668, with a source82 of pressurized liquid. The outer lumen 660 also communicates withports 670 formed on the distal catheter tube end 656 underlying theexpandable body 662. Operation of the source 82 serves to injectpressurized liquid into the body 662 to expand it, in the mannerpreviously described.

As FIG. 8A shows, the physician introduces the tool 650 into thecancellous bone 32. The physician expands the body 662 to create thecavity 84. Once the cavity 84 is formed, the physician begins tocollapse the body 662, while injecting the filling material 96 throughthe nozzle 666. The volume of the cavity 84 occupied by the collapsingbody 662 is progressively filled by the increasing volume of fillingmaterial 96 injected through the nozzle 666.

As earlier described, the collapsing body 662 serves to compact andspread the filling material 96 more uniformly within the cavity 84.Under fluoroscopic monitoring, the physician progressively retracts thedistal end 656 of the tool 650 from the anterior region of the cavity 84toward the outer guide sheath 72, allowing the material 96 to enter andfill the cavity 84.

Upon filling the cavity 84 with the material 96, the physician removesthe outer guide sheath 72, as FIGS. 5P and 5Q show. The incision site issutured or otherwise closed (designated by ST in FIG. 5P).

In time, the filling material 96 sets to a hardened condition within thecavity 84 (see FIGS. 5P and 5Q). The hardened material 96 providesrenewed interior structural support for the cortical bone 28.

The above described procedure, carried out in a minimally invasivemanner, can also be carried out using an open surgical procedure. Usingopen surgery, the physician can approach the bone to be treated as ifthe procedure is percutaneous, except that there is no skin and othertissues between the surgeon and the bone being treated. This keeps thecortical bone as intact as possible, and can provide more freedom inaccessing the interior volume 30 of the vertebral body.

B. Material Selection for the Expandable Body

The material of the body wall 58 can be selected according to thetherapeutic objectives surrounding its use. For example, materialsincluding vinyl, nylon, polyethylenes, ionomer, polyurethane, andpolyethylene tetraphthalate (PET) can be used. The thickness of the bodywall 58 is typically in the range of 2/1000ths to 24/1000ths of an inch,or other thicknesses that can withstand pressures of up to, for example,250-500 psi.

If desired, the material for the wall 58 can be selected to exhibitgenerally elastic properties, like latex. Alternatively, the materialcan be selected to exhibit less elastic properties, like silicone. Usingexpandable bodies 56 with generally elastic or generally semi-elasticproperties, the physician monitors the expansion to assure thatover-expansion and wall failure do not occur. Furthermore, expandablebodies 56 with generally elastic or generally semi-elastic propertieswill require some form of external or internal restraints to assureproper deployment in bone.

For example, expandable bodies 56 with generally elastic properties willexhibit the tendency to backflow or creep into the outer guide sheath 72during their expansion. It is therefore necessary to internally orexternally restrain a body 56 that is subject to creeping, to keep itconfined within the interior bone region. In FIG. 6, an exterior sealingelement 100 is provided for this purpose. In FIG. 6, the sealing element100 takes the form of a movable o-ring.

The physician advances the o-ring 100 along the catheter tube 50 insidethe guide sheath 72 using a generally stiff stylet 102 attached to theo-ring 100. The physician locates the o-ring 100 at or near the distalend 54 of the catheter tube 50 prior to conveying the liquid 82 toexpand the body 56. The o-ring 100 is held in place by the generallystiff stylet 102, which provides a counter force to prevent backwardmovement of the o-ring 100 in the guide sheath 72 as the body 56expands. The o-ring 100 thereby keeps all or a substantial portion ofthe generally elastic body 26 confined inside the interior volume 30.The body 56 thereby serves to compact as much of the cancellous bone 32as possible.

The use of an external sealing element 100 to restrain the expandablebody 56 may not be necessary when relatively inelastic materials areselected for the body 56. For example, the material for the body wall 58can be selected to exhibit more inelastic properties, to limit expansionof the wall 58 prior to wall failure. The body wall 58 can also includeone or more restraining materials, particularly when the body wall 58 isitself made from more elastic materials. The restraints, made fromflexible, inelastic high tensile strength materials, limit expansion ofthe body wall 58 prior to wall failure. Representative examples ofgenerally inelastic wall structures will be described in greater detaillater.

C. Selection of Shape and Size for the Expandable Body

As will also be demonstrated later, when relatively inelastic materialsare used for the body wall 58, or when the body wall 58 is otherwiseexternally restrained to limit its expansion prior to failure, apredetermined shape and size can be imparted to the body 56, when it issubstantially expanded. The shape and size can be predeterminedaccording to the shape and size of the surrounding cortical bone 28 andadjacent internal structures, or by the size and shape of the cavity 84desired to be formed in the cancellous bone 32.

In one embodiment, which is generally applicable for treating bonesexperiencing or prone to fracture, the shape and size of the body 56,when substantially expanded, can be designed to occupy at least about30% of the volume of cancellous bone 32 in the interior volume 30. Abody 56 having a substantially expanded size and shape in the range ofabout 40% to about 99% of the cancellous bone volume is preferred.

In another embodiment, which is applicable for treating bones havingmore localized regions of fracture or collapse caused, for example, byavascular necrosis, the shape and size of the body 56 can be designed tooccupy as little as about 10% of the cancellous bone volume. In thisembodiment, the drilled passage 78 extends directly to the localizedsite of injury, to enable targeted introduction of the body 26.

The shape of the cancellous bone 32 to be compressed, and the presenceof surrounding local anatomic structures that could be harmed ifcortical bone were moved inappropriately, are generally understood bymedical professionals using textbooks of human skeletal anatomy, alongwith their knowledge of the site and its disease or injury. Thephysician is also able to select the materials and geometry desired forthe body 56 based upon prior analysis of the morphology of the targetedbone using, for example, plain films, spinous process percussion, or MRIor CRT scanning. The materials and geometry of the body 56 are selectedto create a cavity 84 of desired size and shape in cancellous bone 32without applying harmful pressure to the outer cortical bone 28 orsurrounding anatomic structures.

In some instances, it is desirable, when creating the cavity 84, to moveor displace the cortical bone 28 to achieve the desired therapeuticresult. Such movement is not per se harmful, as that term is used inthis Specification, because it is indicated to achieve the desiredtherapeutic result. By definition, harm results when expansion of thebody 56 results in a worsening of the overall condition of the bone andsurrounding anatomic structures, for example, by injury to surroundingtissue or causing a permanent adverse change in bone biomechanics.

D. Deployment of Multiple Expandable Bodies

Formation of a desired cavity geometry in cancellous bone 32 using anexpandable body 56 can be accomplished in diverse ways to achieve thedesired therapeutic effect. The foregoing disclosure envisions thedeployment of a single expandable body 56 to compact cancellous bone 32and, by itself, form a cavity 84 having a desired shape and size toreceive a filling material 96.

Alternatively, a cavity 84 having a desired shape and size in cancellousbone 32 can be formed by the deployment of more than one expandable body56 in a targeted region of cancellous bone 32, either sequentially orsimultaneously.

FIG. 9 shows the representative deployment of multiple expandable bodies56A and 56B through a single outer guide sheath 72, which is arranged toprovide transpedicular access. It should be understood that deploymentof multiple expandable bodies can likewise be achieved through an outerguide sheath 72 arranged to provide a posterolateral access, through theside of the vertebral body 26 (as shown as P-L in phantom lines in FIG.9). In FIG. 9, the expandable bodies 56A and 56B are carried by separatecatheter tubes 50A and 50B, which are not joined together.

In the alternative embodiment shown in FIG. 10, a tool 109 comprising anarray 108 of catheter tubes 50A and 50B is provided. Each catheter tube50A and 50B each carries an expandable body 56A and 56B, which are shownin FIG. 10 in a collapsed condition. In FIG. 10, the distal ends of thecatheter tubes 50A and 50B are joined by a connector 106, forsimultaneous deployment through an outer guide sheath 72 into thevertebral body 26, as FIG. 9 shows. As before described, a slidableprotective sheath 73 encloses the bodies 56A and 56B during passagethrough the guide sheath 72. Upon withdrawal of the protective sheath73, expansion of the bodies 56A and 56B, either simultaneously orsequentially, creates a cavity 84. If desired, the connector 106 canpermit relative adjustment of the catheter tubes 50A and 50B, so that,when deployed, one expandable body is located more distal to anotherexpandable body.

For the sake of illustration, FIGS. 9 and 10 show two catheter tubes 50Aand 50B, but more than two catheter tubes can be deployed in thevertebral body 26, either as separate tools (as FIG. 9 shows), or joinedto form a composite array 108 (as FIG. 10 shows).

In FIG. 10, the bodies 56A and 56B of the array 108 have generally thesame geometry, when substantially expanded, thereby providing asymmetric arrangement for compacting cancellous bone 32. A generallysymmetric cavity 84 results.

Alternatively, as shown in FIG. 11, the bodies 56A and 56B possessdifferent geometries when substantially expanded, thereby presenting anasymmetric arrangement for compacting cancellous bone 32. A generallyasymmetric cavity 84 results. By mutually adjusting catheter tubesthrough a connector 106 (as previously described), the distal extensionsof expandable bodies relative to each other can be made to differ,thereby also resulting in asymmetric cavity formation.

The selection of size and shape of the array 108, whether symmetric orasymmetric, depends upon the size and shape of the targeted corticalbone 28 and adjacent internal structures, or by the size and shape ofthe cavity 84 desired to be formed in the cancellous bone 32. Thedeployment of multiple expandable bodies 56 makes it possible to formcavities 84 having diverse and complex geometries within bones of alltypes. Multiple expandable bodies having generally the same geometry canbe deployed in different ways to create cavities of differentgeometries.

It should be appreciated that the various styles of multiple expandablebodies 56 shown in FIGS. 9 to 11 are deployed in a distally straightenedcondition (as FIGS. 10 and 11 show) by using, e.g., a relatively stiff,surrounding sheath 73 (shown in phantom lines in FIG. 10), which ismanipulated in the same as previously described in connection with FIGS.5J(1) and 5J(2). There are, of course, other ways to straighten thebodies 56 for deployment into bone, such as through the use of internalstiffening elements.

Access for expandable bodies 56 can be achieved through multiple accesssites and in many different ways. For example, multiple expandablebodies can access the vertebral body from different regions of atargeted vertebra.

FIG. 12 shows a representative dual transpedicular access, in which twoouter guide sheaths 72A and 72B are used to provide separate access fortwo or more expandable bodies 56A and 56B through different sides of thepedicle 42A and 42B of the vertebral body 26.

FIG. 13 shows a representative dual contra lateral posterolateralaccess, in which two outer guide sheaths 72A and 72B are used to provideseparate access for multiple expandable bodies 56A and 56B fromdifferent lateral sides of the vertebral body 26.

Deployed from dual access sites as shown in FIGS. 12 and 13, themultiple expandable bodies 56A and 56B each forms a cavity 84A and 84B(shown in FIG. 14). The cavities 84A and 84B are transversely spacedwithin the cancellous bone 32. The transversely spaced cavities 84A and84B may adjoin to form a single combined cavity (designated C in FIG.14), into which the filling material 96 is injected. Alternatively, asFIG. 15 shows, the transversely spaced cavities 84A and 84B may remainseparated by a region of cancellous bone (designated by numeral 110 inFIG. 13). In this arrangement, the filling material 96 is injected intomultiple, individual cavities 84A and 84B within the interior volume.

As another example, multiple expandable bodies 56A and 56B can accessthe vertebral body 26 from the same general region of the vertebra. FIG.16 shows a representative dual ipsilateral posterolateral access, inwhich two outer guide sheaths 72A and 72B are used to provide separateaccess from the same lateral sides of the vertebral body 26.

Deployed from these access sites (see FIG. 17), the multiple expandablebodies 56A and 56B form vertically spaced, or stacked, cavities 84A and84B. The vertically spaced cavities 84A and 84B may adjoin to form asingle combined cavity (designated C in FIG. 17), into which the fillingmaterial 96 is injected. Alternatively (see FIG. 18), the verticallyspaced cavities 84A and 84B may be separated by a region of cancellousbone (designated by numeral 110 in FIG. 18), forming multiple individualcavities 84A and 84B within the interior volume, each of which isindividually filled with a filling material 96A and 96B.

By way of another example, FIG. 19 shows a first outer guide sheath 72Aarranged to provide a transpedicular access and a second outer guidesheath 72B to provide a posterolateral access.

Systems for treating bone using multiple expandable bodies can includedirections 79 (see FIG. 12) for deploying the first and secondexpandable bodies. For example, the directions 79 can instruct thephysician to insert a first expandable body into the interior volumethrough a first access path through cortical bone, while inserting asecond expandable body into the interior volume through a second accesspath through cortical bone different than the first access path.

In any of the above-described examples, each guide sheath 72A or 72B canitself accommodate a single expandable body or multiple expandablebodies. The size and shape of the bodies may be the same, or they mayvary, according to the desired objectives of the physician for thetargeted vertebral body.

E. Representative Embodiments of Expandable Bodies to Treat Vertebrae

i. Constrained Donut-Shaped Geometries

FIG. 20 shows a representative embodiment of an expandable body, whichis broadly denoted by the numeral 210. The body 210 comprises a pair ofhollow, inflatable, non-expandable parts 212 and 214 of flexiblematerial, such as PET or Kevlar. Parts 12 and 14 have a suction tube 216therebetween for drawing fats and other debris by suction into tube 216for transfer to a remote disposal location. The catheter tube 216 hasone or more suction holes so that suction may be applied to the open endof tube 216 from a suction source (not shown).

The parts 212 and 214 are connected together by an adhesive which can beof any suitable type. Parts 212 and 214 are doughnut-shaped, as shown inFIG. 20 and have tubes 218 and 220 which communicate with and extendaway from the parts 212 and 214, respectively, to a source of inflatingliquid under pressure (not shown). The liquid expands the body 210 asalready described.

FIG. 21 shows a modified doughnut shape body 280 of the type shown inFIG. 20, except the doughnut shapes of body 280 are not stitched ontoone another. In FIG. 21, body 280 has a pear-shaped outer convex surface282 which is made up of a first hollow part 284 and a second hollow part285. A tube 288 is provided for directing liquid into the two partsalong branches 290 and 292 to inflate the parts after the parts havebeen inserted into the interior volume of a bone. A catheter tube 216may or may not be inserted into the space 296 between two parts of theballoon 280 to provide irrigation or suction. An adhesive bonds the twoparts 284 and 285 together.

FIG. 22 shows another representative embodiment of an expandable body,designated 309. The body 309 has a generally round geometry and threeexpandable body units 310, 312 and 314. The body units 310, 312 and 314include string-like external restraints 317, which limit the expansionof the body units 310, 312 and 314 in a direction transverse to thelongitudinal axes of the body units 310, 312 and 314. The restraints 317are made of the same or similar material as that of the body units 310,312 and 314, so that they have some resilience but substantially noexpansion capability.

A tubes 315 direct liquid under pressure into the body units 310, 312and 314 to expand the units and cause compaction of cancellous bone. Therestraints 317 limit expansion of the body units prior to failure,keeping the opposed sides 377 and 379 substantially flat and parallelwith each other.

ii. Constrained Kidney-Shaped Geometries

FIG. 23 shows another representative embodiment of an expandable body230, which has a kidney-shaped geometry. The body 230 has a pair ofopposed kidney-shaped side walls 232 and a continuous end wall 234. Atube 238 directs liquid into the body to expand it within the vertebralbody.

FIG. 24 shows another representative embodiment of an expandable body242, which also has a kidney-shaped geometry. The body 242 is initiallya single chamber bladder, but the bladder is branded along curved linesor strips 241 to form attachment lines 244 which take the shape ofside-by-side compartments 246 which are kidney shaped as shown in FIG.25. A similar pattern of strips as in 240 but in straight lines would beapplied to a body that is square or rectangular. The branding causes awelding of the two sides of the bladder to occur.

The details of these and other expandable bodies usable to treatvertebral bodies are described in U.S. patent application Ser. No.08/188,224, filed Jan. 26, 1994, which is incorporated herein byreference.

F. Selection of Desired Geometry

The eventual selection of the size and shape of a particular expandablebody or bodies to treat a targeted vertebral body 26 is based uponseveral factors. When multiple expandable bodies are used, the totalcombined dimensions of all expandable bodies deployed, whensubstantially expanded, should be taken into account.

The anterior-posterior (A-P) dimension (see FIG. 26) for the expandablebody or bodies is selected from the CT scan or plain film or x-ray viewsof the targeted vertebral body 26. The A-P dimension is measured fromthe internal cortical wall of the anterior cortex to the internalcortical wall of the posterior cortex of the vertebral body. In general,the appropriate A-P dimension for the expandable body or bodies is lessthan this anatomic measurement.

The appropriate side to side dimension L (see FIG. 26) for an expandablebody or bodies is also selected from the CT scan, or from a plain filmor x-ray view of the targeted vertebral body. The side to side distanceis measured between the internal cortical walls laterally across thetargeted vertebral body. In general, the appropriate side to sidedimension L for the expandable body is less than this anatomicmeasurement.

The lumbar vertebral body tends to be much wider in side to sidedimension L then in A-P dimension. In thoracic vertebral bodies, theside to side dimension and the A-P dimensions are almost equal.

The height dimensions H of the expandable body or bodies (see FIG. 26)is chosen by the CT scan or x-ray views of the vertebral bodies aboveand below the vertebral body to be treated. The height of the vertebralbodies above and below the vertebral body to be treated are measured andaveraged. This average is used to determine the appropriate heightdimension of the chosen expandable body.

The dimensions of expandable body or bodies for use in vertebrae arepatient specific and will vary across a broad range, as summarized inthe following table:

Posterior Side to Height (H) (A-P) Side Dimension Dimension Dimension ofTypical of Typical (L) of Typical Expandable Expandable ExpandableVertebra Body or Body or Body or Type Bodies Bodies Bodies Lumbar 0.5 cmto 0.5 cm to 0.5 cm to 4.0 cm 4.0 cm 5.0 cm Thoracic 0.5 cm to 0.5 cm to0.5 cm to 3.5 cm 3.5 cm 4.0 cm

A preferred expandable body 56 for use in a vertebral body is stackedwith two or more expandable members of unequal height (see FIG. 26),where each member can be separately inflated through independent tubesystems. The total height of the stack when fully inflated should bewithin the height ranges specified above. Such a design allows thefractured vertebral body to be returned to its original height in steps,which can be easier on the surrounding tissue, and it also allows thesame balloon to be used in a wider range of vertebral body sizes.

II. Treatment of Long Bones

Like vertebrae, the interior regions of long bones substantiallyoccupied by cancellous bone can be treated with the use of one or moreexpandable bodies. FIG. 43 shows representative regions of the humanskeleton 600, where cancellous bone regions of long bones can be treatedusing expandable bodies. The regions include the distal radius (Region602); the proximal tibial plateau (Region 604); the proximal humerus(Region 606); the proximal femoral head (Region 608); and the calcaneus(Region 610).

As for vertebral bodies, expandable bodies possess the importantattribute of being able, in the course of forming cavities bycompressing cancellous bone, to also elevate or push broken orcompressed cortical bone back to or near its normal anatomic position.This is a particularly important attribute for the successful treatmentof compression fractures or cancellous bone fractures in theappendicular skeleton, such as the distal radius, the proximal humerus,the tibial plateau, the femoral head, hip, and calcaneus.

Representative examples of expandable bodies for the treatment ofcancellous bone regions of long bones will be next described.

A. Expandable Body for the Distal Radius

The selection of an appropriate expandable to treat a fracture of thedistal radius (Region 602 in FIG. 43) will depend on the radiologicalsize of the distal radius and the location of the fracture.

FIGS. 27 and 28 show a representative expandable body 260 for use in thedistal radius. The body 260, which is shown deployed in the distalradius 252, has a shape which approximates a pyramid but more closelycan be considered the shape of a humpbacked banana. The geometry of thebody 260 substantially fills the interior of the space of the distalradius to compact cancellous bone 254 against the inner surface 256 ofcortical bone 258.

The body 260 has a lower, conical portion 259 which extends downwardlyinto the hollow space of the distal radius 252. This conical portion 259increases in cross section as a central distal portion 261 isapproached. The cross section of the body 260 is shown at a centrallocation (FIG. 27), which is near the widest location of the body 260.The upper end of the body 260, denoted by the numeral 262, converges tothe catheter tube 288 for directing a liquid into the body 260 to expandit and force the cancellous bone against the inner surface of thecortical bone.

The shape of the body 260 is determined and restrained by tufts formedby string restraints 265. These restraints are optional and provideadditional strength to the body 260, but are not required to achieve thedesired configuration.

The body 260 is placed into and taken out of the distal radius in thesame manner as that described above with respect to the vertebral bone.

Typical dimensions of the distal radius body vary as follows:

The proximal end of the body 260 (i.e. the part nearest the elbow) iscylindrical in shape and will vary from 0.4×0.4 cm to 1.8×1.8 cm.

The length of the distal radius body will vary from 1.0 cm to 12.0 cm.

The widest medial to lateral dimension of the distal radius body, whichoccurs at or near the distal radio-ulnar joint, will measure from 0.5 cmto 2.5 cm.

The distal anterior-posterior dimension of the distal radius body willvary from 0.4 to 3.0 cm.

B. Expandable Body for Proximal Humerus Fracture

The selection of an appropriate expandable body 266 to treat a givenproximal humeral fracture (Region 606 in FIG. 43) depends on theradiologic size of the proximal humerus and the location of thefracture.

FIG. 29A shows a representative embodiment of an expandable body 266 foruse in the proximal humerus 269. The body 266 is spherical forcompacting the cancellous bone 268 in a proximal humerus 269. Ifsurrounding cortical bone has experienced depression fracture, expansionof the body 266 also serves to elevate or move the fractured corticalbone back to or near its anatomic position before fracture.

A mesh 270, embedded or laminated and/or winding, may be used to form aneck 272 on the body 266. A second mesh 270 a may be used to conform thebottom of the base 272 a to the shape of the inner cortical wall at thestart of the shaft. These mesh restraints provide additional strength tothe body 266, but the configuration can be achieved through molding ofthe body.

The body 266 has a catheter tube 277 into which liquid under pressure isforced into the body to expand it to compact the cancellous bone in theproximal humerus. The body 266 is inserted into and taken out of theproximal humerus in the same manner as that described above with respectto the vertebral bone.

Typical dimensions of the expandable body 266 shown in FIG. 29A forproximal humerus fracture vary as follows:

The spherical end of the body will vary from 0.6×0.6 cm to 3.0×3.0 cm.

The neck of the proximal humeral fracture body will vary from 0.5×0.5 cmto 3.0×3.0 cm.

The width of the base portion or distal portion of the proximal numeralfracture body will vary from 0.5×0.5 cm to 2.5×2.5 cm.

The length of the body will vary from 3.0 cm to 14.0 cm.

FIG. 29B shows another representative embodiment of an expandable body266′ for use in the proximal humerus 269. Instead of being spherical,the body 266′ shown in FIG. 29B has a generally cylindrical geometry forcompacting the cancellous bone 268 in a proximal humerus 269.Alternatively, the cylindrical body 266′ can be elongated to form anelliptical or football-shaped geometry. Typical dimensions for acylindrical or elliptical body vary from 0.6 cm to 3.0 cm in diameter to3.0 cm to 14.0 cm in length.

C. Expandable Body for Proximal Tibial Plateau Fracture

The selection of an expandable body to treat a given tibial plateaufracture (Region 604 in FIG. 43) will depend on the radiological size ofthe proximal tibial and the location of the fracture.

FIG. 30A shows a representative expandable body 280 for treating atibial plateau fracture. The body 280 may be introduced into the tibiafrom any direction, as desired by the physician, for example, from thetop, or medial, lateral, anterior, posterior, or oblique approach. InFIG. 30A, the body 280 has been introduced into cancellous bone 284 fromthe anterior side of the tibia 283 and is shown position in one side 282of the tibia 283.

The body 280, when substantially inflated (as FIG. 30A shows), compactsthe cancellous bone in the layer 284 surrounding the body 280. If thetibia plateau has experienced depression fracture, expansion of the body280 also serves to move the tibia plateau back to or near its anatomicelevation before fracture, as FIG. 30A shows. Fractures on both themedial and lateral sides of the tibia can be treated in this manner.

As FIG. 30B shows, the body 280 has a pair of opposed sides 285 and 287.The sides 285 and 287 are interconnected by restraints 288, which passthrough the body 280. FIG. 30C shows the tied-off ends 291 of therestraints 288.

The restraints 288 can be in the form of strings or flexible members ofany suitable construction. The restraints 288 limit expansion of thebody 280 prior to failure. The restraints 288 make the sides 285 and287, when the body 280 is substantially expanded, substantially parallelwith each other and, thereby, non-spherical.

A tube 290 is coupled to the body 280 to direct liquid into and out ofthe body to expand it. The body is inserted into and taken out of thetibia in the same manner as that described above with respect to thevertebral bone. FIG. 30C shows a substantially circular configurationfor the body 280, although the body 280 can also be substantiallyelliptical, as FIG. 31 shows.

Other geometries and configurations can also be used. For example, asFIG. 32 shows, two or more expandable bodies 280(1), 280(2), and 280(3)can be stacked one atop another to produce a different cavity geometryand to enhance plateau fracture displacement. The multiple bodies280(1), 280(2), and 280(3) can comprise separate units or be joinedtogether for common deployment. When deployed as separate units, thebodies 280(1), 280(2), and 280(3) can enter through the same accesspoint or from different access points.

As another example, as FIG. 33 shows, the body 280′ can assume an eggshape when substantially inflated, to form a cavity and reshape brokenbones. Other geometries, such as cylindrical or spherical, can also beused for the same purpose.

Typical dimensions of the body 280 for treating proximal tibial plateaufracture vary as follows:

The thickness or height of the body will vary from 0.3 cm to 5.0 cm.

The anterior-posterior (front to back) dimension will vary from 1.0 cmto 6.0 cm.

The medial to lateral (side-to-side) dimension will vary from 1.0 cm to6.0 cm.

FIGS. 44 and 45 show multiple expandable zones 614 and 616 deployed incancellous bone 620. One zone 614 serves as a platform to confine anddirect the expansion of the other zone 616. For the purpose ofillustration, FIGS. 44 and 45 show the multiple zones 614 and 616 usedfor this purpose to treat a tibial plateau fracture 622.

In the embodiment shown in FIGS. 44 and 45, the zones 614 and 616comprise separate expandable bodies. It should be appreciated, however,that the zone 614 and 616 can comprise parts of a single expandablebody.

In the illustrated embodiment (as FIG. 44 shows), the first expandablebody 614 is deployed through a first outer guide sheath 618(1) intocancellous bone 620 below the fracture 622. As FIG. 44 shows, whensubstantially expanded, the first body 614 expands more along itshorizontal axis 624 (i.e., in a side-to-side direction) than along itsvertical axis 626 (i.e., in an top-to-bottom direction). The greaterexpanded side-to-side geometry of the first body 614 compacts cancellousbone in a relatively thin region, which extends substantially across theinterior volume 628 occupied by the first body 614. The geometric limitsof the body 614 will typically fall just inside the inner cortical wallsof the proximal tibia, or whatever bone in which the first body 614 isdeployed.

The expanded first body 614 creates a barrier 630 within the interiorregion 628. Due to the less expanded top-to-bottom geometry of the firstbody 614, a substantially uncompacted region 632 of cancellous bone isleft above the body 614, which extends from the formed barrier 630upward to the fracture 622. In a representative deployment, theuncompacted region 632 extends about 2 cm below the tibial plateaufracture 622.

As FIG. 44 shows, a second expandable body 616 is deployed through asecond outer guide sheath 618(2) into the uncompacted region 632 leftbetween the first body 614, when substantially expanded, and thetargeted tibial plateau fracture 622.

As FIG. 45 shows, the second expandable body 616 has a geometry,substantially like that shown in FIGS. 30A to 30C. When substantiallyinflated, the second body 616 compacts a large percentage of thecancellous bone in the region 632 above the first expandable body 614.The presence of the barrier 630, which the expanded first body 614creates (see FIG. 46 also), prevents expansion of the second body 616 ina direction away from the tibial platform fracture 622. Instead, thebarrier 630 directs expansion of the second body 616 toward the fracture622. Buttressed by the barrier 630, the expansion of the body 616 isdirected against the fractured plateau 622, restoring it to its normalanatomic position, as FIGS. 45 and 46 show.

It should be appreciated that one or more expandable bodies can be usedas platforms or barriers to direct the expansion of one or more otherexpandable bodies in other localized interior bone regions. The barriermakes possible localized cavity formation in interior bone regions. Useof the barrier preserves healthy regions of cancellous bone, whiledirecting the main compacting body toward localized fractures orlocalized regions of diseased cancellous bone.

D. Expandable Body for Femoral Head

The size of an expandable body for use in the femoral head (Region 608in FIG. 43) is chosen based upon the radiological or CT scan size of thehead of the femur and the location and size of the avascular necroticbone.

FIG. 34 shows a representative embodiment of an expandable body 300introduced inside the cortical bone 302 of the femoral head. As FIG. 34shows, the femoral head is thin at the outer end 304 of the femur andincreases in thickness at the lower end 306 of the femur. A tube 309directs liquid to expand the body 300. The tube 309 extends along thefemoral neck and into the femoral head. The expandable body 300 compactsthe cancellous bone 307 in this bone region, while also moving fracturedcortical bone back to or near its normal anatomic position.

The femoral head is generally spherical in configuration, and the body300 can have either a hemispherical (see FIG. 35) as well as sphericalgeometry (as FIG. 34 shows). The hemispherical shape is maintained inFIG. 34 by bonding overlapping portions of the body 300, creating pleats300 b.

The body 300 is inserted into and taken out of the femoral head in thesame manner as that described with respect to the vertebral bone.

Typical dimensions of an expandable body for use in treating the femoralhead vary as follows:

The diameter of the expandable body will vary from 0.5 cm to up to 4.5cm. The dimensions of the hemispherical body (FIG. 35) are the same asthe those of the spherical body (FIG. 34), except that approximately onehalf is provided.

E. Expandable Body for Prevention of Hip Fracture

Patients with bone density in the hip (Region 612 in FIG. 43) below athreshold value are at increased risk of hip fracture, and lowerdensities create greater risk. Patient selection is done through a bonedensity scan.

FIG. 36A shows a representative embodiment of an expandable body 410having a “boomerang” geometry for use in preventing hip fracture. Whensubstantially expanded (as FIG. 36A shows), the body 410 forms acylinder, which gradually bends in the middle, like a boomerang, andextends from about 0.5 cm from the end of the femoral head 411 throughthe femoral neck 412 and down into the proximal femoral diaphysis 413about 5 to 7 cm past the lesser trochanter 414.

Expansion of the body 410 is limited to achieve the described geometryby rings 430 of inelastic material. The rings 430 are held in a spacedapart relationship along one side of the body 410 by attachment to aninelastic band 416, which runs the length of that side of body 410. Therings 430 are held in a farther spaced apart relationship along theopposite side of the body 410 by attachment to another, longer inelasticband 417, which runs the length of the opposite side of the body 410. Atube 419 conveys liquid to inflate the body 410.

Prior to deployment within the body, the body 410 is collapsed androlled up and held against the inflation tube 419 using, for example,with frangible connectors that will break as the body is subject toexpansion. To deploy the body 410 into the hip, the surgeon uses a powerdrill under radiographic guidance to create a cavity 420, which is, forexample, about 4 to 6 mm wide starting at the lateral femoral cortex 421and proceeding into the femoral head 411. The body 410 is deployedthrough a guide sheath 423, following the cavity 420. The body 410 isdeployed, prior to expansion, facing the lesser trochanter 414, so thatexpansion occurs toward the femoral diaphysis 413, and not toward thegreater trochanteric region 422.

The expansion of the body 410 is guided by the rings 430 and bands 416and 417, which cause bending of the body 410 downward into the lessertrochanter 414. Optionally, a second cavity can be drilled down into thediaphysis 413, starting from the same entry point or from the otherside.

The body length is chosen by the physician to extend about 0.5 cm fromthe end of the femoral head, through the femoral neck and into theproximal femoral diaphysis, usually about 4 to 8 cm below the lessertrochanter. The body diameter is chosen by measuring the inner corticaldiameter of the femoral neck (the most narrow area) and subtracting 0.5cm. The preferred dimensions of the body 410 are a total length of 10-20cm and a diameter of about 1.0-2.5 cm.

Patients having the lowest bone densities in the femoral head mayrequire greater compacting in the femoral head, which may, for example,be provided by using two bodies, one after the other: the bent body 410followed by the femoral head body (inserted at the same point andexpanded prior to inserting any supporting material). Alternatively, thebent body 410 may be adapted to have a distal portion that approximatesthe shape of the femoral head body.

The geometry of the single, restrained body 410 can be approximated bymultiple expandable bodies deployed separately, or coupled together, orstacked together. FIG. 36B shows a representative embodiment of the useof multiple expandable bodies in the hip region.

As FIG. 36B shows, a first expandable body 410(1) is introduced througha first outer guide sheath 423(1) in the proximal lateral cortex of thefemoral shaft. The first body 419(1) is deployed across the femoral neck480 into the femoral head 482.

A second expandable body 410(2) is introduced through a second outerguide sheath 423(2) in the greater trochanter 422 of the femur. Thefirst body 419(1) is deployed in the direction of the femoral diaphysis413.

Other approaches can be used. For example, one body can be introducedthrough the femoral neck 480, and the other body can be introduced alongthe shaft of the femur.

One or both of the bodies 410(1) and 410(2) can include externalrestraints to limit expansion, in the manner described with regard tothe body 410. Expansion of the bodies 410(1) and 410(2) compactscancellous bone to form a cavity having a geometry approximating thatformed by the single body 410.

F. Expandable Body for Calcaneus Fracture

The size of an expandable body for use in treating fracture of thecalcaneus (heel bone) (Region 610 in FIG. 43) is chosen based upon theradiological or CT scan size of the calcaneus and the location and sizeof the fracture.

FIGS. 37A and 37B show a representative expandable body 450 for treatingfracture of the calcaneus 452. A tube 464 conveys liquid into the body450 to expand it.

In FIG. 37A, the body 450 is deploy into the calcaneus 452 by aposterior approach, through the tuberosity. Other approaches can beused, as desired by the physician. A power drill opens a passage 466through the tuberosity into the calcaneus. An outer guide sheath 470 ispositioned within the passage 466, abutting the posterior of thecalcaneus, in the manner previously described in obtaining access to avertebral body. The body 450 is introduced through the guide sheath 470and formed passage 466 into the calcaneus.

Expansion of the body 450 is limited within the confines of thecalcaneus by inelastic peripheral bands 454 (see FIG. 37B). The bands454 constrain expansion of the body 450 to an asymmetric, pear-shapedgeometry, best shown in FIG. 37B. The pear-shaped geometry has a majordimension H1 occupying the region of the posterior facet 454. The majordimension H1 is located here, because the part of the calcaneus mostlikely to require elevation and realignment during expansion of the body450 is the depressed part of the posterior facet 454 of the calcaneus,where the posterior facet 454 abuts the talus 456.

The pear-shaped geometry has a smaller, minor dimension occupying theregion of the anterior facet 458 of the calcaneus, near thecalcaneal-cuboid joint 460, between the calcaneus and cuboid bone 462.

Expansion of the body 410 compacts cancellous bone 470 within thecalcaneus 452. The expansion also lifts a depression fracture of theposterior facet 454 back to or near its original anatomic elevationadjacent the talus 456. When collapsed and removed, the body 410 leavesa cavity in cancellous bone into which filling material can beintroduced in the manner previously described.

FIG. 38 shows another representative embodiment of an expandable body450′ for use in treating fractures in the calcaneus. The body 450′ inFIG. 38 has a more spherical or egg-shaped geometry than the pear-shapedbody 450 shown in FIG. 37B. Like the pear-shaped body 450, the body450′, when expanded within the calcaneus, forms a cavity withincancellous bone and realigns fractured cortical bone at or near itsnormal anatomic position.

III. Selection of Other Expandable Bodies (Further Overview)

Different sizes and/or shapes of expandable bodies may be used at sitesnot specified above, such as the jaw bones, the midshaft of the arm andleg bones, the cervical vertebral bodies, the foot and ankle bones, thepelvis, the ribs, and the like.

The choice of the shape and size of a expandable body takes into accountthe morphology and geometry of the site to be treated. As before stated,the shape of the cancellous bone to be compressed, and the localstructures that could be harmed if bone were moved inappropriately, aregenerally understood by medical professionals using textbooks of humanskeletal anatomy along with their knowledge of the site and its diseaseor injury. Precise dimensions for a given patient can be furtherdetermined by X-ray of the site to be treated.

As one general guideline, the selection of the geometry of theexpandable body should take into account that at least 40% of thecancellous bone volume needs to be compacted in cases where the bonedisease causing fracture (or the risk of fracture) is the loss ofcancellous bone mass (as in osteoporosis). The preferred range is about30% to 90% of the cancellous bone volume. Compacting less of thecancellous bone volume can leave too much of the diseased cancellousbone at the treated site. The diseased cancellous bone remains weak andcan later collapse, causing fracture, despite treatment.

Another general guideline for the selection of the geometry of theexpandable body is the amount that the targeted fractured bone regionhas been displaced or depressed. The expansion of the body within thecancellous bone region inside a bone can elevate or push the fracturedcortical wall back to or near its anatomic position occupied beforefracture occurred.

However, there are times when a lesser amount of cancellous bonecompaction is indicated. For example, when the bone disease beingtreated is localized, such as in avascular necrosis, or where local lossof blood supply is killing bone in a limited area, the expandable bodycan compact a smaller volume. This is because the diseased arearequiring treatment is smaller.

Another exception lies in the use of an expandable body to improveinsertion of solid materials in defined shapes, like hydroxyapatite andcomponents in total joint replacement. In these cases, the body shapeand size is defined by the shape and size of the material beinginserted.

Yet another exception is the delivery of therapeutic substances, whichwill be described in greater detail later. In this case, the cancellousbone may or may not be diseased or adversely affected. Healthycancellous bone can be sacrificed by significant compaction to improvethe delivery of a drug or growth factor which has an importanttherapeutic purpose. In this application, the size of the expandablebody is chosen by the desired amount of therapeutic substance sought tobe delivered. In this case, the bone with the drug inside is supportedwhile the drug works, and the bone heals through exterior casting orcurrent interior or exterior fixation devices.

Generally speaking, providing relatively inelastic properties for theexpandable body, while not always required, is nevertheless preferredwhen maintaining a desired shape and size within the bone is important,for example, in bone graft placement or in a vertebral body, where thespinal cord is nearby. Using relatively inelastic bodies, the shape andsize can be better predefined, taking into account the normal dimensionsof the outside edge of the cancellous bone. Use of relatively inelasticmaterials also more readily permits the application of pressures equallyin all directions to compress cancellous bone. Still, substantiallyequivalent results can usually be achieved by the use of multipleexpandable bodies having highly elastic properties, if expansion iscontrolled by either internal or external restraints, as previouslydisclosed.

IV. Confinement of Filling Material

A. Dual Stage Filling

FIGS. 39A to 39D show a multiple stage process for introducing fillingmaterial into a cavity formed by an expandable body in cancellous bone.The process is shown in association with treating a vertebral body. Thisis for the purpose of illustration. It should be appreciated that theprocess can be used in the treatment of all bone types.

Use of the multi-stage process is indicated when pre-examination of thetargeted bone reveals that a portion of the cortical wall 28 hasfractured or failed (as FIG. 39A shows at the anterior region of thevertebral body 26). The failed cortical wall 28 creates gaps and cracks(designated G in FIG. 39A). Typically, remnant chips 500 of the failedcortical bone 28 may lay in the cancellous bone 32 in the region wherecortical wall failure has occurred. Filling material can flow or seepthrough these gaps or cracks C outside of the interior volume of thebone.

The process begins at the point where the outer guide sheath 72 has beenpositioned and the guide pin removed in the manner previously described.The physician introduces a first expandable body 502 into the cancellousbone 32 near the failed cortical bone region, as FIG. 39A shows. Thefirst expandable body 502 is sized, when substantially expanded, tooccupy a relatively small volume (i.e., less than about 20%) of thevolume of cancellous bone 32 in interior volume 30.

The physician expands the first expandable body 502, compacting arelatively small region of cancellous bone. Upon collapse and removal ofthe first body 502, a small cavity 504, caused by the compaction,remains (as FIG. 39B shows).

The physician introduces the injector tip 90 and injects an aliquot offilling material 96(1) (for example, about 1 cc to about 9 cc) into theformed small cavity 504 (as FIG. 39B shows).

In a short time interval (before the filling material 96(1) is allowedto substantially set and harden), the physician withdraws the injectortip 90 and introduces a second expandable body 506 into the cancellousbone 32 (see FIG. 39C). The second expandable body 506 is larger thanthe first body 502. The second body 506 is sized to create the desiredgeometry for the therapeutic main cavity 508 in cancellous bone 32.

As FIG. 39C shows, expansion of the second body 506 displaces theearlier injected aliquot of filling material 96(1) in the cavity 504toward the failed cortical wall region. The aliquot of filling material96(1) will envelop remnant chips 500 of cortical bone lying in its path.The material 96(1) and enveloped chips 500 are pressed against thefailed cortical bone region as expansion of the second body 506progresses. The first aliquot of filling material 96(1) will begin toset and harden as the main therapeutic cavity 508 is being formed by theexpansion of the second body 506. The second body 506 is collapsed andremoved, leaving the main cavity 508.

As FIG. 39D shows, the first aliquot of filling material 96(1) providesa viscous or (in time) hardened boarder region along the anterior edgeof the cavity 508. As subsequent injection of additional fillingmaterial 96(2) into the main cavity 508 proceeds, as FIG. 39D shows, theviscous or hardened boarder region 96(1) impedes passage of theadditional filling material 96(2) as it fills the main cavity 508. Theviscous or hardened boarder region 96 (1) serves as a dam, keeping theadditional filling material 96(2) entering the main cavity 508 fromseeping from the vertebral body 26.

B. Interior Mesh

FIGS. 40 and 41 show the use of an interior mesh 510 in association withthe introduction of filling material into a cavity formed by anexpandable body in cancellous bone. The mesh 510 is shown in associationwith treating a vertebral body, but it should be appreciated that theprocess can be used in the treatment of all bone types.

Use of the mesh 510 is indicated when pre-examination of the targetedbone reveals a failed cortical bone region (as FIG. 41 shows at theanterior region of the vertebral body 26), coupled with the lack ofenough bone matter, due to advanced disease or a complex fracture, toadequately fill the failed cortical bone region by compacting using anexpandable body. Flowable cement material can flow or seep through theunfilled gaps or cracks (designated G in FIG. 41) present in the failedcortical bone region.

The mesh 510 comprises a woven structure made from biocompatiblematerial like Goretex™ material, Nitinol™ material, or Dacron™ material.The mesh presents a surface area, which is about ⅓rd to ½ of theinterior area of the main therapeutic cavity 84 formed by the selectedexpandable body.

Before deploying the injector tip 90 into the formed cavity 84 (which isdeployed in FIG. 41 by posterolateral access), the physician drapes themesh 510 over the tip 90, as FIG. 40 shows. As FIG. 41 shows, theviscous flow of filling material 96 injected from the tip 90 carries themesh 510 into the cavity 84 in advance of the filling material 96. Themesh 510 is urged by the filling material 96 into contact with theanterior region of the bone, including the failed cortical bone region.The mesh 510, permeated with viscous material 96 and resting over thefailed cortical bone region, impedes passage of filling material, untilhardening occurs.

V. Delivery of Therapeutic Materials

A cavity created in cancellous bone by any of the expandable bodiesdescribed above can be filled with a medically-appropriate formulationof a drug or a growth factor.

An expandable body can compact infected cancellous bone to create aspace which can be filled with the antibiotic gel in an open orminimally invasive procedure. The cavity places and holds the requiredamount of drug right at the site needing treatment, and protects thedrug from being washed away by blood or other fluids.

Not only can the dose be optimized, but additional doses can be appliedat later times without open surgery, enhancing the therapeutic outcome.If the required cavity for the optimal drug dose weakens the bone, thebone can be protected from future fracture with a cast or with currentinternal or external metal or plastic fixation devices.

The therapeutic substance put into bone may act outside the bone aswell. A formulation containing chemotherapeutic agent could be used totreat local solid tumors, localized multiple myeloma or even a nearbyosteosarcoma or other tumor near that bone.

The cavity formed by an expandable body can be filled with anappropriate supporting material, like acrylic bone cement orbiocompatible bone substitute, which carries a therapeutic substance.Alternatively, the therapeutic substance can be separately deliveredbefore injection of the filling material. Thus, using an expandablebody, the physician is able to treat a fracture while also delivering adesired therapeutic substance (like an antibiotic, bone growth facer orosteoporosis drug) to the site.

As an alternative, to deliver therapeutic substances, bodies can bedipped in a medical formulation (often a dry powder, liquid or gel)containing a medically-effective amount of any desired antibiotic, bonegrowth factor or other therapeutic agent to coat the body with theabove-mentioned substance before it is inserted into a bone beingtreated. Optionally, the body can be wholly or partially expanded beforethe coating is performed. optionally, the coated body can be dried withair or by other means when the applied formulation is wet, such as aliquid or a gel. The body is refolded as required and either usedimmediately or stored, if appropriate and desired. Coated on the body,therapeutic substances can be delivered while cancellous bone is beingcompressed, or with an additional body once the cavity is made.

The methods described above can also be used to coat Gelfoam or otheragents onto the body before use. Inflating the Gelfoam-coated bodyinside bone will further fill any cracks in fractured bone not alreadyfilled by the compressed cancellous bone.

FIGS. 42A to 42C schematically illustrate one system and method fordelivering a therapeutic substance to the bone using an expandable body529. The body 529 is carried at the end of the catheter tube 530, whichconveys liquid to expand the body 529, as previously described.

As shown in FIG. 42A, the expandable body 529, in a substantiallyexpanded condition, is stabilized with a clip 531 that couples thecatheter tube 530 to a wire 532. As shown in FIG. 42B, a measured amountof gel formulation containing the desired amount of substance 533 isuniformly dispensed from a container 534, preferably in thin lines 535,onto the outer surface of the body 536. The coating substance can be thedesired compound alone in its natural state (solid, liquid or gas) or inan appropriate formulation, including a dry powder, an aerosol or asolution. As shown in FIG. 42C, the coated body 537 is collapsed andallowed to dry until the gel sets. Alternatively, the body 536 can alsobe coated without prior expansion. The optional drying time will, ofcourse, depend on the nature of the compound and its formulation. Thecoated body 237 is suitable for packaging for use by a surgeon.

Delivering a therapeutic substance on the outside of expandable bodyused to compact the bone, or with an expandable body introduced afterthe bone is compacted, is qualitatively different than puttingformulated drug into the cavity. When delivered while the bone iscompressed, the therapeutic substance becomes incorporated into thecompacted bone. This can serve as a way to instantly formulate a slowrelease version of the substance.

The cavity formed by the expandable body can be filled with anappropriate supporting material, like acrylic bone cement orbiocompatible bone substitute, as before described.

Medically-effective amounts of therapeutic substances are defined bytheir manufacturers or sponsors and are generally in the range of 10nanograms to 50 milligrams per site, although more or less may berequired in a specific case.

For example, the cavity can accommodate a typical dose of theantibiotic, gentamicin, to treat a local osteomyelitis (bone infection).A typical dose is about 1 gram, although the therapeutic range forgentamicin is far greater, from 1 nanogram to 100 grams, depending onthe condition being treated and the size of the area to be covered. Amedically-suitable gel formulated with appropriate gel materials, suchas Polyethylene glycol, can contain 1 gram of gentamicin in a set volumeof gel, such as 10 cc.

Other antibiotics that can be used to treat bone infection include, forexample, ancef, nafcillin, erythromycin, tobramycin, and gentamicin.Typical bone growth factors are members of the Bone MorphogeneticFactor, Osteogenic Protein, Fibroblast Growth Factor, Insulin-LikeGrowth Factor and Transforming Growth Factor alpha and beta families.Chemotherapeutic and related agents include compounds such as cisolatin,doxcrubicin, daunorubicin, methotrexate, taxol and tamoxifen.Osteoporosis drugs include estrogen, calcitonin, diphosphonates, andparathyroid hormone antagonists.

VI. Delivery of Biomaterials

A cavity created in cancellous bone by any of the expandable bodiesdescribed above can also be filled with biomaterials.

Biomaterials, which do not flow into the formed cavity, likehydroxyapatite granules or bone mineral matrix, can be pushed down atube with a long pin whose diameter is slightly more narrow than theinner-diameter of the outer guide sheath, using the minimally-invasiveprocedure. During open surgery, the physician can approach the bone inthe same way.

If the biomaterial to be inserted does not flow and should not be pushedinto the cavity through the guide sheath (as in the case of thehydroxyapatite block, because that can cause damage), the physician canform the cavity using a minimally invasive approach, then punch a holeusing standard tools (such as a punch, gouge or rasp) into one side ofthe cortical bone to allow insertion of the block.

VII. Bone Marrow Harvesting

Any of the expandable bodies described above can also be used in theharvesting of bone marrow for diagnostic or therapeutic purposes, forexample, in the diagnosis of multiple myeloma or in the treatment ofadvanced cancers with bone marrow transplants.

FIG. 47 shows a system 700 for harvesting bone marrow in a bone-marrowproducing bone 702. The bone 702, which is shown diagrammatically inFIG. 47, can comprise, for example, the pelvis, or a vertebral body, ora distal radius.

The system 700 employs a bone marrow harvesting tool 704. The tool 764includes a catheter tube 706, which carries an expandable body 708 atits distal end. The tool 704 can be deployed into the bone 702 using aminimally invasive approach, as previously described.

The catheter tube 706 has three concentric and independent lumens 710,712, and 714 (see FIG. 48). The outer lumen 710 communicates with theinterior of the body 78 and is coupled to a source 718 of an inflationliquid. The middle lumen 712 communicates with a source 720 of rinseliquid and a distal opening 716 on the catheter tube 706. The centerlumen 714 communicates with a collection container 722 and a seconddistal opening 724 on the catheter tube 706.

The body 708 is deployed in a substantially collapsed condition, asalready described. Inflation liquid, which is preferably radiopaque, isconvey from the source 718 into the body 708 to expand it.

As FIG. 48 shows, the body 708 is constrained by selection of relativelyinelastic materials or by exterior restraints (as previously described)to assume an elongated shape. Expansion of the body 708 creates arelatively shallow area of compaction 726 in cancellous bone 728 along arelatively long length. The size and shape of the body 708 will dependupon the geometry of the harvest site and the amount of bone marrowrequired. In long bones, like the distal radius, and in bones withnarrow width but large area, such as the ribs or pelvis, the body 728 isshaped to compress a large area but not a great depth of cancellous bone728.

As FIG. 48 also shows, as the body 708 expands, rinse liquid, which canbe saline or another suitable biocompatible liquid, is conveyed from thesource 720 into the area 726 (shown by arrows 730 in FIG. 48). The rinseliquid loosens up biological components (such as red blood cells, bonecells, and immune-.beta. cells) within the defined area 726, formingcomponent-rich suspension 732.

The body 708 is collapsed, and suction is applied through the lumen 714.The suction draws the component-rich suspension 732 from the area 726into the collection container 722.

The above sequence of expansion, rinsing, collapse, and aspiration canbe repeated to collect additional component-rich suspension 732 in thecontainer 722. The position of the expandable body 708 in the bone 702can be changed, if desired, to maintain a component-rich suspension 732for harvesting.

Use of the expandable body 708 to form the long but shallow compactionarea 726 permits the harvest of a significant concentration oftherapeutic biological components with less damage to bone thatconventional harvesting methods. If desired, standard casts or otherfixation devices can be applied to the bone 702 after bone marrowharvesting until the bone 702 heals.

The features of the invention are set forth in the following claims.

1. A method comprising the steps of: providing a compression structurehaving an inflatable body portion through the interior of which anelongated member extends; inserting the compression structure intocancellous bone; and inflating the body portion of the insertedcompression structure to compress the cancellous bone and create acavity therein.
 2. The method of claim 1 further comprising the stepsof: deflating the body portion; and removing the compression structurefrom the cavity.
 3. The method of claim 1 further comprising the stepof: disposing a filler material in the cavity.
 4. The method of claim 3wherein: the filler material is a bone cement material.
 5. The method ofclaim 1 wherein: the elongated member has a hollow tubularconfiguration.
 6. The method of claim 5 wherein: the elongated member isa suction tube.
 7. The method of claim 1 wherein: the inflatable bodyportion comprises at least one balloon.
 8. The method of claim 1wherein: the inflatable body portion comprises a plurality of joinedballoons.
 9. The method of claim 1 wherein: the inflatable body portionis inflatable transverse to the elongated member a distance greater thanthe distance that the inflatable body portion is inflatable parallel tothe elongated member.
 10. The method of claim 1 wherein: the inflatablebody portion is formed from a flexible, non-expandable material.
 11. Themethod of claim 1 wherein: the elongated member has opposite endportions, each of which extends outwardly beyond an exterior surfaceportion of the body portion.
 12. The method of claim 1 wherein: theinflatable body portion is formed from an expandable material.
 13. Themethod of claim 1 wherein: the inflatable body portion has associatedtherewith a structure for limiting its inflation distance in a selecteddirection.
 14. The method of claim 1 wherein: the inflatable bodyportion has a flattened configuration and is sized to be operativelyinserted into and inflated within cancellous bone within a vertebralbody.
 15. The method of claim 1 wherein: the elongated memberlongitudinally extends substantially completely across the interior ofthe inflatable body portion.
 16. The method of claim 1 wherein: theinflating step is performed using an inflation tube communicating withthe interior of the inflatable body portion, and the elongated memberextends substantially parallel to the inflation tub